Corals Call In Fish

Corals call in fish according to ScienceNOW and New Scientist 8 November 2012 and Science 9 November 2012: Vol. 338 pp. 804-807 DOI: 10.1126/science.1225748. Coral reefs and seaweed both need light to survive, but seaweed can easily overgrow corals and block the light, and some seaweeds are poisonous to corals. Scientists studying the tropical coral Acropora nasuta have found that when it is overgrown by seaweed it sends out a chemical signal that attracts goby fish, which eat the seaweed. To test whether the fish were responding to the coral signals they placed gobies in tanks with a seaweed named turtleweed, which grows on coral reefs and damages them. The fish were indifferent to it when they were in a tank with the seaweed alone, but when placed in a tank with coral and seaweed they were attracted to the coral and removed the seaweed. The scientists summarised their findings as: “Thus, the gobies serve as bodyguards for host corals, and the coral chemically cues gobies to attract them to the site of coral-algal contact where they begin removing the alga (seaweed) within minutes of seaweed contact”. The researchers suggest this mutualistic relationship is the “marine parallel to terrestrial ant-plants, in that the host provides shelter and food in return for protection from natural enemies”.

Editorial Comment: Have you noticed that no creatures can exist “by themselves”, but all are interdependent on a whole range of other creatures. These mutualistic relationships are a reminder that the living world really functions on cooperation, rather than competition. Darwin blew it right there! Chemical signalling between plants and animals is not a new find. Many grasses manufacture chemicals which deter grazing animals when they are being over-grazed and need time to re-grow. Furthermore, mutualistic and symbiotic relationships between different living things are proving to be the norm, rather than the exception. This is exactly what you would expect because living things were created as part of predesigned ecosystems where they were designed to interact with one another in a way that enhanced the life of all, rather than compete so “the fittest would eliminate” the unfit. As such they serve as evidence that the world was created in a short time and was originally very good. The researchers make no comment about how they believe this mutual relationship came about, but we wonder how they think corals survived in the evolutionary timetable as both coral and seaweed supposedly evolved millions of years before vertebrate fish and the sea grasses were supposedly here before the corals. What an impossible uphill battle. We also wonder how they believe corals evolved the genes for producing the chemical signals while the fish evolved the genes for responding to the signal just in time for the corals to survive eh? Unlikely, since the fish in this case show no sign of exclusively depending on the corals for their survival. One cannot be responsible for the other, but each is useless without the other. (Ref. ecology, mutualism, ichthyology)